Man is thus unique, with some other primates, in having adrenals that secrete large amounts of the precursor steroids dehydroepiandrosterone sulfate (DHEA-S) and dehydroepiandrosterone (DHEA) which are converted into androstenedione (4-dione) and then into active androgens and/or estrogens in peripheral tissues (Labrie et al., In: Important Advances in Oncology. Edited by V. T. de Vita, S. Hellman, S. A. Rosenberg. J. B. Lippincott, Philadelphia, 193-217, 1985; Labrie, Mol. Cell. Endocrinol., 78: C113-C118, 1991; Labrie, et al., In Signal Transduction in Testicular Cells. Ernst Schering Research Foundation Workshop. Edited by V. Hansson, F. O. Levy, K. Taskén. Springer-Verlag, Berlin-New York (Suppl. 2), pp. 185-218, 1996; Labrie et al., Steroids, 62: 148-158, 1997). In a recent study (Labrie, et al., J. Clin. Endocrinol. Metab., 82: 2403-2409, 1997), we have described a dramatic decline in the circulating levels of dehydroepiandrosterone (DHEA), DHEA-sulfate (DHEA-S), androst-5-ene-3β,17β-diol (5-diol), 5-diol-S, 5-diol fatty acid esters, and androstenedione in both men and women between the ages of 20 and 80 years.
Despite the marked fall in endogenous androgens in women during aging, the use of androgens in post-menopausal women has been limited mainly because of the fear of an increased risk of cardiovascular disease as based upon older studies showing an unfavorable lipid profile with androgens. Recent studies, however, have shown no significant effect of combined estrogen and androgen therapy on the serum levels of cholesterol, triglycerides, HDL, LDL, and HDL/LDL ratio when compared to estrogen alone (Sherwin et al., Am. J. Obstet. Gynecol., 156: 414-419, 1987). In agreement with these observations, we have shown that DHEA, a compound having a predominantly androgenic influence, has apparently no deleterious effect on the serum lipid profile (Diamond, et al., J. Endocrinol., 150: S43-S50, 1996). Similarly, no change in the concentrations of cholesterol, its subfractions or triglycerides, over a treatment with estradiol alone has been observed after 6 months of therapy with estradiol+testosterone implants (Burger et al., Br Med. J. Clin. Res. Ed., 294: 936-937, 1987). It should be mentioned that a study in man has shown an inverse correlation between serum DHEA-S and low density lipoproteins (Parker et al., Science, 208: 512-514, 1980). More recently, a correlation has been found between low serum testosterone and DHEA and increased visceral fat, a parameter of higher cardiovascular risk (Tchernof et al., Metabolism, 44: 513-519, 1995).
Five-diol is a compound biosynthesized from DHEA through the action of reductive 17β-hydroxysteroid dehydrogenase (17β-HSD) and is a weak estrogen. It has an 85-fold lower affinity than 17β-estradiol (E2) for the estrogen receptor in rat anterior pituitary gland cytosol (Simard and Labrie, J. Steroid Biochem., 26: 539-546, 1987), further confirming the data obtained on the same parameter in human myometrial and breast cancer tissue (Kreitmann and Bayard, J. Steroid Biochem., 11: 1589-1595, 1979; Adams et al., Cancer Res., 41: 4720-4926, 1981; Poulin and Labrie, Cancer Res., 46: 4933-4937, 1986). However, at concentrations well within the range of the plasma levels found in adult women, 5-diol enhances cell proliferation and progesterone receptor levels in human mammary tumor ZR-75-1 cells (Poulin and Labrie, Cancer Res., 46: 4933-4937, 1986) and increases the estrogen-dependent synthesis of the 52 kDa glycoprotein in MCF-7 cells (Adams et al., Cancer Res., 41: 4720-4926, 1981).
As mentioned above, it is known that the serum levels of DHEA, DHEA-S and 5-diol decrease with age and correspondingly, that there is a dramatic age-dependent reduction in the formation of androgens and estrogens in peripheral target tissues. Such changes in DHEA-S and DHEA secretion result in a marked decrease in the biochemical and cellular functions stimulated by sex steroids. As a result, DHEA and DHEA-S have recently been used in the treatment of a variety of conditions which are associated with decrease and/or imbalance in the levels of sex steroids.
Osteoporosis, a condition which affects both men and women, is associated with a decrease in androgens and estrogens. Estrogens have been shown to decrease the rate of bone degradation while androgens have been shown to build bone mass. However, estrogen replacement therapy commonly used against osteoporosis requires the addition of progestins to counteract the endometrial proliferation and the risk of endometrial cancer induced by estrogens. Moreover, since both estrogens and progestins are thought to increase the risk of breast cancer (Bardon et al., J. Clin. Endocrinol. Metab., 60: 692-697, 1985; Colditz et al., N. Engl. J. Med., 332: 1589-1593, 1995), the use of estrogen-progestin replacement therapy is accepted by a limited number of women and, usually, for too short periods of time.
Several studies suggest that osteoporosis is a clinical manifestation of androgen deficiency in men (Baran et al., Calcif. Tissue Res. 26: 103-106, 1978; Odell and Swerdloff, West J. Med. 124: 446-475, 1976; Smith and Walker, Calif. Tissue Res. 22 (Suppl.): 225-228, 1976). Androgen therapy, as observed with nandrolone decanoate, has been found to increase vertebral bone mineral density in postmenopausal women (Need et al., Arch. Intern. Med., 149: 57-60, 1989). Therapy of postmenopausal women with nandrolone increased cortical bone mineral content (Need et al., Clin. Orthop. 225: 273-278, 1987). Androgenic side-effects, however, were recorded in 50% of patients. Such data are of interest since while almost all present therapies are limited to a reduction of bone loss, an increase in bone mass was found with the use of the anabolic steroid nandrolone. A similar stimulation of bone formation by androgens has been suggested in a hypogonadal male (Baran et al., Calcif. Tissue Res. 26: 103, 1978). A stimulation of bone formation in postmenopausal women treated with DHEA for 12 months is reported in Labrie et al. (J. Clin. Endocrinol. 82: 3498-3505, 1997).
DHEA (450 mg/kg, b.w., 3 times a week) markedly delayed the appearance of breast tumors in C3H mice which were genetically bred to develop breast cancer (Schwartz, Cancer Res. 39: 1129-1132, 1979). Moreover, the risk of developing bladder cancer was found to be increased in men having lower serum DHEA levels (Gordon et al., Cancer Res. 51: 1366-1369, 1991).
U.S. patent application U.S. Pat. No. 5,550,107 relates to a method of treatment of breast and endometrial cancer in susceptible warm-blooded animals which may include inhibition of ovarian hormonal secretion by surgical means (ovariectomy) or chemical means (use of an LHRH agonist, e.g. [D-Trp6, des-Gly-NH210]LHRH ethylamide, or antagonist) as part of a combination therapy. Antiestrogens, androgens, progestins, inhibitors of sex steroid formation (especially of 17β-hydroxysteroid dehydrogenase- or aromatase-catalyzed production of sex steroids), inhibitors of prolactin secretion and of growth hormone secretion and ACTH secretion are discussed. A counterpart thereof has been published under international publication number WO 90/10462.
In addition, cardiovascular diseases have been associated with decreased serum levels of DHEA and DHEA-S and both DHEA and DHEA-S have been suggested to prevent or treat these conditions (Barrett-Connor et al., N. Engl. J. Med. 315: 1519-1524, 1986).
In aged Sprague-Dawley rats, Schwartz (in Kent, Geriatrics 37: 157-160, 1982) has observed that body weight was reduced from 600 to 550 g by DHEA without affecting food intake. Schwartz (Cancer 39: 1129-1132, 1979) observed that C3H mice given DHEA (450 mg/kg, 3 times a week) gained significantly less weight and grew older than the control animals, had less body fat and were more active. The reduction in body weight was achieved without loss of appetite or food restriction. Furthermore, DHEA could prevent weight gain in animals bred to become obese in adulthood (in Kent, Geriatrics 37: 157-160, 1982).
DHEA administration to lean Zucher rats decreased body weight gain despite increased food intake. Treated animals had smaller fat pads thus, overall, suggesting that DHEA increases food metabolism, resulting in lower weight gain and fat accumulation (Svec et al., Proc. 2nd Int. Conf. Cortisol and Anti-Cortisols, Las Vegas, Nev., USA, p. 56 abst., 1997).
Obesity was found to be improved in the Avy mutant mouse (Yen et al., Lipids 12: 409-413, 1977) and in the Zucker rat (Cleary and Zisk, Fed. Proc. 42: 536, 1983). DHEA-treated C3H mice had a younger appearance than controls (Schwartz, Cancer Res. 39: 1129-1132, 1979).
DHEA reduced the incidence of atherosclerosis in cholesterol-fed rabbits (Gordon et al., J. Clin. Invest. 82: 712-720, 1988; Arad et al., Arteriosclerosis 9: 159-166, 1989). Moreover, high serum concentrations of DHEA-S have been reported to protect against death from cardiovascular diseases in men (Barrett-Connor et al., N. Engl. J. Med. 315: 1519-1524, 1986). Circulating levels of DHEA and DHEA-S have thus been found to be inversely correlated with mortality from cardiovascular disease (Barrett-Connor et al., N. Engl. J. Med. 315: 1519-1524, 1986) and to decrease in parallel with the diminished immune competence (Thoman and Weigle, Adv. Immunol. 46: 221-222, 1989). A study in man has shown an inverse correlation between fetal serum DHEA-S and low density lipoprotein (LDL) levels (Parker et al., Science 208: 512, 1980).
Uses of DHEA as well as the benefits of androgen and estrogen therapy are discussed in International Patent Publication WO 94/16709.
Correlations observed in the prior art are not believed to suggest treatment or prophylactic methods that are effective, or as free of undesirable side-effects, as are combination therapies disclosed here.